In reply to GridNorth:
Germany, France, Spain, Sweden, Belgium, England, Scotland. True, there are a mish mash of eye bolt and hanger types(I've even seen Petzl hangers that looked ok from below, but were rotten on the top!). Like I've said above, it's not often that I've felt the need to double up on the draws but very occasionally I do.
I can't particularly recall when I have used a screwgate in this kind of situation, as I know I've used screwgates when I've ran out of quickdraws, but I would if I needed to. You don't carry any screwgates sport climbing?, I'll usually take two or three, one on the end of the sling for securing at the lower off and a couple for just incase!.
I'd say in the times I've felt the need to double up, I've spotted this from being below or level with the bolt, reading that the route trickles left a bit, or right a bit, if I'm in doubt, I'll double it up, to me it's all part of reading, or trying to read the route as you climb it.